Electrode



United States Patent fine 2,848,41 l Patented Aug. 19, 1958 ELECTRODEForest H. Hartzell, Dayton, Ohio Application April 12, 1955, Serial No.500,730

3 Claims. (Cl. 204-290) This invention relates to electrodes and moreparticularly to a composite electrode for use in electrolytic cells forelectroplating and the like.

In electroplating operations in which it is desired to effect theelectrodeposition on an article to be plated of such metals as silver,nickel, copper, etc., an anode of such metal may be suspended in anelectrolyte in which the article to be plated is also suspended andconnected to a source of current to be the cathode of an electrolyticcell. In such case, the metal to be deposited is displacedelectrolytically from the anode, goes into solution in the electrolyte,and is redeposited as a plating on the surface of the article to beplated as the cathode. When the electrodeposition of other metals, suchas chromium, is desired, however, the metal to be deposited isintroduced into the electrolytic cell as a solution of a metallic salt.In such cases, an anode of a dissimilar metal is used, such anodeincluding the property of being resistant to electrolytic decompositionin the cell.

Since the quantity of metal electrolytically deposited on the .article:to be plated in a given time is proportional to the current passedthrough the anode and the electrolyte, the anode should be of highelectroconductivity.

Since metals of high electroconductivity, Such as copper, areelectrolytically decomposed if used as the anode even when chromium saltsolutions are used as the electrolyte for the purpose of plating anarticle with chromium, such high conductivity anodes may not givesatisfactory results in a chromium plating operation because copper fromthe anode will be deposited onto the article to be plated along withchromium from the electrolyte solution. Metals which are resistant toelectrolytic decomposition in such a chromium plating cell, however,generally possess substantially less electroconductivity. For example,an anode .comprising lead or an alloy -of lead with tin or antimony isnot subject to electrolytic decomposition.

Such an .anode, however, .has a vhigh resistance and a conductivity of(as little .as 6% or 7% .of that of, for example, copper. Such higherresistance vmay require a sufliciently high current density as to causeheating of the anode .actually to the point of vaporization of theelectrolyte. Also, the current, seeking the path of least resistance mayleave the anode in the .area of the surface of the electrolyte \to amuch greater extent than at the lower levels of :the anode therebyproducing uneven plating on the article to be plated and actual burningor corrosion of the anode at'the area of the electrolyte surface.

I-f it .is attempted to combat these several disadvantages by, forexample, providing an electrode of a material with suitable resistanceto electrolytic (decomposisionand encasing in the electrode a conductingcore of highly conductive metal such as copper for the purpose ofconducting the currentflsubstantially throughout the electrode --formore even distribution therefrom .in the plating bath, :it :has beenfound that the core portion itself may be subject to undesiredelectrolytic action in the bath upon erosion and/or chemical action ofthe bath on the lead and/or as a result of pin holes, eroded pitting, orsimilar imperfections in the encasing lead electrode in manufacture oruse.

According to this invention, however, an electrode is provided for suchelectroplating operations having a main body portion of suitable metalsubstantially resistant to electrolytic decomposition in theelectroplating cell, a core portion of a metal of high conductivity forconducting the current substantially uniformly to the electrode, and aprotective sheath resistant to chemical attack and surrounding the coreportion to protect it from contact with any portions of the electrolytewhich may erode or otherwise penetrate the main body portion of theelectrode. An electrode according to this invention also includes an airgap or insulating space between the core portion and the electrode atthe por tion thereof generally in the area of the liquid level ofelectrolyte in the electroplating cell to combat the natural tendency ofthe current to be discharged adjacent the surface of the electrolyte toa greater extent than the lower levels in the electroplating bath.

It is, accordingly, a principal object of this invention to provide anelectrode for use in electroplating operations of the characterdescribed and having a'main -body portion of a metal resistant toelectrolytic decomposit-ion in "the electroplating bath, a highlyconductive core portion, and a protective sheath to protect said coreportion from attack by elements of the electrolytic bath which maypenetrate the main body portion.

Another object of this invention is to provide an electrode of thecharacter described having an insulated space F between. the coreportion and the main body portion in the area of the liquid level in theelectroplating bath.

A further object of this invention is to provide an electrode of thecharacter described having ,a main body portion, a core portion ofhigher electroconductivity than said main body portion and encasedthereby, and .a protective sheath for said core portion, with means forintegrating and directly connecting said core portion with said mainbody portion at a plurality of points .along the lengths thereof.

Still another object of this invention is .to provide in av compositeelectrode of the character described means for assuring the uniformelectric contact between the highly conductive core and the encased mainbody port-ion of the electrode notwithstanding the encasement of thecore portion in a protective sheath therefor. Y

A still further object of this invention is to provide a method forassembling an electrode of the character described having a sheathedhighly conductive core portion-embedded in a main body portion ofdissimilar metal.

Still another object of this invention vis to provide a method formanufacturing .a composite electrode of the character described in whicha core portion is embedded in a main body portion and electricallyunited therewith substantially throughout the lengths thereofnotwithstanding the provision of a protective sheath substantiallyencasing said core portion as embedded in said :main

body portion.-

Still a further object of this invention is to provide 131.1 electrodeof the character described having a main body portion comprising lead, ahighly conductive core .comprising copper, a protective sheath ofchemically resistant steel substantially encasing said core portionWithin said main body portion, andapluralityofdirect contact pointsintegral with said main body portion :and penetrating said sheath infused direct contact relation with said copper core portion.

Other objects and advantages of this invention will be apparent from thefollowing description, the attached drawing and the appended claims.

In the drawing,

Fig. 1 is a perspective view of an electrode embodying this invention;

Fig. 2 is a plan view partly broken away showing a partly assembledelectrode embodying this invention;

Fig. 3 is a partial longitudinal section of an electrode embodying thisinvention with some parts being broken away;

Fig. 4 is a cross section of an electrode embodying this invention alongthe lines 44 of Fig. 2;

Fig. 5 is a cross section of an electrode embodying this invention alongthe line 55 of Fig. 2;

Fig. 6 is a cross section of an electrode embodying this invention alongthe line 6-6 of Fig. 2;

Fig. 7 is a cross section of an electrode embodying this invention alongthe line 7-7 of Fig. 2; and

Fig. 8 is a perspective view of one sheath member of an electrodeembodying this invention.

Referring to the drawing, in which like parts are indicated by likereference numerals throughout the several views, Fig. 1 shows anelectrode embodying this invention having a main body portion 10 and acore portion 11 embedded in the main body portion 10. A hook 12 isprovided at one end of the core portion for suspending the electrode inthe electroplating bath and for providing .a contact member for theconnection of the electrode to a source of electric current in knownmanner, the hook ,12 being encased in the metal of the body portion 10except for a contact gap 14 to leave a portion of the core 11 exposed.

Considering an electroplating operation in which the electrolyte orplating bath includes a solution of chromium salts for theelectrodeposition of a chromium plating on an article to be plated, themain body portion 10 preferably comprises a metal resistant toelectrolytic attack in said bath, such as lead or an alloy of lead withtin or antimony, while the core portion 11 preferably comprises a highlyconductive material such as copper. While longitudinally ofsubstantially uniform thickness, the main body portion 10 preferably hasan irregular cross section including a plurality of points, ridges, oredges 13 from which the electric current will more readily flow into theplating solution.

As indicated in Fig. 2, the core 11 extends substantially throughout thelength of the electrode and includes a plurality of holes 15. As shownin Figs. 3 and 6-7, the core 11 is encased in a sheath comprising aU-shaped channel member 20 and a fiat member 21 each of which extendsthroughout the greater portion of the length of the core 11 from thebottom thereof up to approximately the point indicated at 22. Thereabovethe core 11 is encased in an inverted U-shaped sheath member 25 (Fig. 8)the width of which is substantially greater than the core 11 so that thesides 26 of member 25 are laterally spaced apart from the core memberleaving an insulating air space 27 therebetween. Member 25 and the airgaps 27 are positioned longitudinally within the main body portion 10 ofthe electrode so as to extend from just above the normal liquid level inthe electroplating bath to just below that level eifecting insulationbetween the core 11 and the main body portion 10 adjacent the liquidlevel in the area where current has the greatest tendency to flownonuniformly from the electrode at the liquid level in the bath.

The uppermost portion of the core 11 above the air gaps 27, is alsoencased in a sheath comprising U-shaped member 30 and the flat extension31 on member 25. As indicated in Figs. 3 and 7, the sheath member 20 isprovided with a plurality of holes 32 substantially coincident with theholes in the core 11, which holes 32 are preferably chamfered asindicated at 33 and of somewhat larger diameter than the holes 15. Thevarious sheath members 20, 21, 25, and 30 comprise material 4 such assteel resistant to chemical attack by elements in the electroplatingbath.

The assembly and fabrication of a composite electrode embodying thisinvention may be described as follows: The main body portion 10 is castor extruded in a manner to obtain maximum density and freedom from pinholes and/ or other imperfections which may in use provide a point oferosion, chemical attack, o other failure which would admit ofpenetration by the electrolyte into the main body portion 10. Alongitudinal groove 35 is provided in the main body portion 10 in theside thereof opposite to the points or ridges 13. This groove isdimcnsioned to accommodate the core 11 and its surrounding sheathmembers 20, 21, etc. That portion of groove 35 coincident with the airgaps 27 is made wider, as indicated in Figs. 2 and 5, to accommodate themember 25 and to provide space for the air spaces 27 surrounding thecore 11.

The U-shaped sheath members 20 and 30 are inserted into the groove 35with the holes 32 in member 20 against the bottom of the groove. Thecore member 11 is then inserted into the groove and into the upturnedchannel members 20 and 30 with the holes 15 in member 11 substantiallycoincident with the holes 32 in member 20. The holes 15 and 32 are thenfilled with molten lead or lead alloy of which main body member 10 iscomposed. This molten metal flows through the holes 15 and 32 to providea fused unifying contact with the main body portion 10 as indicated inFigs. 3 and 7, the chamfered edges 33 and larger diameter of the holes32 aiding in this unification. Preferably both the copper core 11 andthe sheath member 20 are tinned before assembly to aid in producing thecompletely fused unifying contact upon the addition of the molten leador lead alloy. Additionally, prior to filling the holes 15 and 32 withmolten metal, the tinned sheath 20 and core 11 are burned with a torchin position to produce a soldered or fused connection throughout.

With the holes 15 and 32 substantially filled with molten lead or leadalloy, the sheath members 21 and 25 are inserted into the groove 35 tooverlie the core 11 and complete the sheathing thereof. The solderingand/or addition of molten lead or lead alloy over the core 11 to fillthe holes 15 and 32 may leave a residual layer 34 7 of lead between thecore 11 and sheath member 21, which is positioned to overlie theupturned sides of sheath member 20. As indicated by a comparison ofFigs. 5 and 6, the sheath members 20 and 21 encase and contact the core11 whereas the sides 26 of sheath member 25 are spaced from the core 11to provide the air spaces 27 therearound. Thereafter additional moltenlead or lead alloy is poured into the groove 35 above the sheath members21 and 25 and beyond the bottom end 36 of the core 11 to complete theencasing of the core member 11 and its protective sheath in the mainbody portion 10.

It will accordingly be seen that, in use, an electrode embodying thisinvention presents a number of advantages. The current is conductedthrough the highly conductive core 11 substantially throughout thelongitudinal extent of the main body portion 10. Because the thicknessof the main body portion 10 surrounding the highly conductive core 11 issubstantially uniform throughout the length of the electrode, theresistance to current flow from the electrode is substantially uniformat all depths in the plating bath thereby providing for substantiallyuniform deposition of the plating metal on the article to be plated. Theprincipal exception to the foregoing is in the area of the air spaces 27where the insulating effect of the air spaces is provided to increasethe resistance of current flow from the core portion 11 to the main bodyportion 10 to combat the natural tendency of the current more readily toleave the electrode adjacent the liquid level of the electroplatingbath.

The core portion 11 is substantially completely encased in a chemicallyresistant sheath to protect it from electrolytic or chemical action byelements of the electroplating bath which may inevitably penetrate themain body portion due to erosion, chemical action, pin holes, and/orimperfections therein. Notwithstanding this, however, direct electriccontact is maintained between the core portion and the main body portionsub: stantially throughout the lengths thereof by the plurality ofdirect contact points east through the holes and 32, as well as bydirect electric contact through the steel sheath 20, 21, etc. In thisconnection, it should be noted that, whereas the lead or lead alloy mainbody portion 10 has a conductivity approximately 6% or 7% of the coppercore portion 11, the chemical resistant steel of the sheath members 20,21, etc., may have a conductivity approximately twice that of the mainbody portion 10, thus assuring reduced uniform resistance to currentflow between the highly conductive core 11 and the electrolysisresistant main body portion 10 substantially throughout the lengthsthereof.

Although the cross sectional contour of an electrode embodying thisinvention has been illustrated as embodying the ridges or protrusions13, it will be understood that other contours may be provided in knownmanner. The size of the electrode, also, may be varied according toprinciples well understood in the art. Satisfactory results have beenachieved, however, with a main body portion 10 of approximately 3 inchesin Width at its point of greatest width, 1% inch in thickness at itspoint of greatest thickness, and inches long, and with the core member11 being approximately inch wide and A inch thick.

While the methods and forms of apparatus herein described constitutepreferred embodiments of the invention, it is to be understood that theinvention is not limited to these precise methods. and forms ofapparatus, and that changes may be made therein without departing fromthe scope of the invention which is defined in the appended claims.

What is claimed is:

1. In a method for constructing a composite electrode having a coreportion and a main body portion of dissimilar metals for use in anelectrolytic cell having a fluid electrolyte, the steps comprisingforming a main body portion for said electrode including a-metalresistant to electrolysis in said cell, forming in said main bodyportion a longitudinal groove substantially throughout the lengththereof, the width and depth of said groove being larger than thedimensions of said core portion, forming a generally U-shaped sheath forsaid core portion of a metal difierent from said core portion and saidmain body portion and resistant to chemical attack in said electrolyticcell, forming a plurality of coincident holes through said core portionand said U-shaped sheath, assembling said sheath and said core portionin said groove, uniting said sheath and core portion with said main bodyportion by introducing molten metal through said holes, covering theexposed upper surface of said core portion with an additional sheathmember, and substantially filling said groove above said additionalsheath member with molten metal to form said composite electrode.

2. In a method for constructing a composite electrode having a coreportion and a main body portion of dissimilar metals for use in anelectrolytic cell having a fluid electrolyte, the steps comprisingforming said main body portion for said electrode including a metalresistant to electrolysis in said cell, forming in said main bodyportion a longitudinal groove substantially throughout the lengththereof, the width and depth of said groove being larger than thedimensions of said core portion, forming a generally U-shaped sheath forsaid core portion of a metal diiferent from said core portion and saidmain body portion and resistant to chemical attack in said electrolyticcell, tinning said sheath and said core portion for fused unificationthereof, forming a plurality of coincident holes through said coreportion and said U-shaped sheath, assembling said sheath and said coreportion in said groove with said core portion within said sheath andseparated thereby from said main body portion, heating said assembledelements effecting fused integration of said core portion, said sheathportion and said main body portion at their respective adjacentsurfaces, introducing molten metal into said groove over said coreportion and through said holes uniting said sheath and core portion withsaid main body portion, covering said core portion with an additionalsheath member for encasing said core portion substantially completely,and substantially filling said groove above said additional sheathmember with molten metal to form said composite electrode.

3. A composite electrode for use in an electrolytic cell having a liquidelectrolyte in which said electrode is suspended and at least partiallyimmersed, comprising in combination an elonagted main body portionincluding a metal resistant to electrolytic attack by said electrolyte,a core within said main body portion and extending substantiallythroughout the length thereof, said core including a metal of greaterconductivity than said main body portion for conducting electricalcurrent substantially throuhgout said main body portion, a protectivesteel sheath encasing said core for protection thereof against chemicalattack by substances in said electrolyte which penetrate said main bodyportion, and means spacing said core from said main body portionadjacent one end thereof and generally positioned to extend from aboveto below the level of said liquid electrolyte, and a plurality of directcontact points penetrating said steel sheath. and integrally unitingsaid main body portion with said core through said sheath.

References Cited in the file of this patent UNITED STATES PATENTS

3. A COMPOSITE ELECTRODE FOR USE IN AN ELECTROLYTIC CELL HAVING A LIQUID ELECTRLYTE IN WHICH ELECTRODE IS SUSPENDED AND AT LEAST PARTIALLY IMMERSED, COMPRISING IN COMBINATION AN ELONGATED MAIN BODY PORTION INCLUDING A METAL RESISTANT TO ELECTRLYTIC ATTACK BY SAID ELECTROLYTE, A CORE WITHIN SAID MAIN BODY PORTION AND EXTENDING SUBSTANTIALLY THROUGHOUT THE LENGTH THEREOF, SAID CORE INCLUDING A METAL OF GREATER CONDUCTIVITY THAN SAID MAIN BODY PORTION FOR CONDUCTING ELECTRICAL CURRENT SUBSTANTIALLY THROUGHOUT SAID MAIN BODY PORTION, A PROTECTIVE STEEL SHEATH ENCASING SAID CORE FOR PROTECTION THEREOF AGAINST CHEMICAL ATTACK BY SUBSTANCES IN SAID ELECTROLYTE WHICH PENETRATE SAID MAIN BODY PORTION, AND MEANS SPACING SAID CORE FROM SAID MAIN BODY PORTION ADJACENT ONE END THEREOF AND GENERALLY POSITIONED TO EXTEND FROM ABOVE TO BELOW THE LEVEL OF SAID LIQUID ELECTROLYTE, AND A PLURALITY OF DIRECT CONTACT POINTS PENETRATING SAID STEEL SHEATH AND INTEGRALLY UNITING SAID MAIN BODY PORTION WITH SAID CORE THROUGH SAID SHEATH. 